The 2012 Buick LaCrosse may need to be reprogrammed by GM for smoother transmission shifts. Photo Credit: GM

Dear Doctor: I own a 2012 Buick LaCrosse. From the day I left the showroom, I have been complaining about the way the transmission shifts in 1st & 2nd speeds. With light acceleration 1st & 2nd speeds won't shift, until the engine revolutions have reached 4,000 rpms. When I step harder on the gas pedal those gears won't shift until the rpms are over 6,000. The dealer said they have had many complaints on this, but cannot correct it until they get an updated program from GM. Is there another way to correct this problem? -- Joe

Dear Joe: The transmission is controlled by the computer and sensor inputs under all driving conditions. To change the shifting points the computer does need to be reprogrammed. There are many Technical Service Bulletins on your car. This is not a bad thing, as there are areas that need updating that GM has been made aware of. In the meantime, you can lift off the gas pedal slightly and the transmission should upshift. To run the engine up to 6,000 rpms is not good for the engine or transmission. Have the dealer test-drive the sedan and if they have the same shifting problem, they should give you a loaner until the computer can be reprogrammed.

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Dear Doctor: My daughter owns a 2005 Mercury Mariner with 60,000 miles. She's experiencing a problem upon start up. The "check gas cap" message illuminates on the dash, which then goes out after driving for a few minutes. I've checked the tightness of the cap and have made sure that when filling up she does it with the engine off. Is there anything else I should be doing? -- Tony

Dear Tony: The gas cap message indicates an EVAP leak in the fuel system. The technician will need to connect a scan tool and look at the sensor value information before the engine start up. This information will show the technician what sensor is out of range and where the problem is located.

Dear Doctor: I have a 1998 Chevy S-10 pickup truck with 2.2-liter engine and over 160,000 miles. Over the course of a week I experienced three episodes where the engine would sputter and respond slowly to throttle, as if running out of gas. During this time I couldn't shift out of 3rd gear or reach a speed of 30 mph. Over a month later everything is running fine with no replaced parts. Could a fuel injection cleaner have caused this to happen? The previous time I used this additive there were no problems. -- Harry

Dear Harry: You did not mention if the "check engine" light came on. When the computer cannot read a sensor value it will set the "check engine" light. There is no connection with any type of cleaner that would cause this problem. I tell my customers to use 93-octane instead of gas additives if they have any concerns about fuel additives. The intermittent problem you have is connected with the electrical side of the fuel delivery not the fuel supply (fuel pump). If the truck has an external fuel filter, then I would suggest checking or replacing it. Mass air flow meters and weak ignition coils are common issues.

Dear Doctor: After driving for long distances in my 2004 Infiniti i35 with air conditioning running the passenger side carpeting becomes soaking wet. The drains are clear and the a/c is draining while the motor is running and standing still. We have been to the dealer on many occasions and since they can't replicate the problem they can't rectify the problem. Your suggestions are appreciated. -- Gloria and Ed

Dear Gloria and Ed: I see this problem on a lot of vehicles and the a/c drain is clear. The problem is the actual drain tube is too short and the water drips back into the passenger compartment. I looked on the Identifix web site and found the quick and easy repair is to add a 4-inch spark plug wire boot onto the drain. In some cases the seal between the heater box and firewall needs to be resealed with silicone. Alldata.com has perfect view of the heater box and drain.

Dear Doctor: I have a 2012 Mazda3 w/Skyactiv engine. Whenever I first drive the car and put it into drive it does a "jack-rabbit" start. I would like to know what causes this and if there is anything I can do to prevent this, Thank you. -- Eric

Dear Eric: I drove the new Mazda3 with Skyactiv and the automatic transmission for a week and enjoyed the test drive, but it does take so getting used to. When first started all engines will idle at a higher engine speed. As the engine warms up the idle will drop down. Secondly, the gear ratio in the transmission is low to give you the extra power during take off from a stop. -- Junior Damato, Motor Matters